1. Field
The present application relates generally to wireless communications, and more specifically to methods and systems to enable identification of femto cells or access point base stations with passive assistance from a macro cellular wireless network.
2. Background
Wireless communication systems are widely deployed to provide various types of communication (e.g., voice, data, multimedia services, etc.) to multiple users. As the demand for high-rate and multimedia data services rapidly grows, there lies a challenge to implement efficient and robust communication systems with enhanced performance.
In recent years, users have started to replace fixed line communications with mobile communications and have increasingly demanded great voice quality, reliable service, and low prices.
In addition to mobile phone networks currently in place, a new class of small base stations has emerged, which may be installed in a user's home and provide indoor wireless coverage to mobile units using existing broadband Internet connections. Such personal miniature base stations are generally known as access point base stations, or, alternatively, Home Node B (HNB) or Femto cells. Typically, such miniature base stations are connected to the Internet and the mobile operator's network via DSL router or cable modem.
One of the issues with mobile stations and femto cells is how the Mobile Station (MS) (sometimes also called User Equipment—UE, or Access Terminal—AT) finds a femto cell when it is operating on a macro-cellular network. The mobile station may be on a frequency different than one used by the femto cell. The femto cell may reuse one of several available carrier frequencies. If the mobile is not on that very frequency when using the macro cellular network, it would miss the femto cell, and continue to operate on the macro cell, although it is within the coverage of the femto cell. Additionally, even if there is a way to find a femto cell, mobile may not be authorized to access it (access may be restricted). The problem can be further complicated by the fact that new femto cells are put in operation all the time.
Currently proposed solutions use pilot beacons to signal on other frequencies the presence of the femto cell on the frequency used by femto cells. This approach has a weakness because it adds to interference on the other frequencies. Other proposals include constant periodic search for femto cells, which can hurt battery life. Accordingly, there is a need in the art for mobile devices to be able to locate femto cells with passive assistance from macro cellular wireless network.